Explosively actuated expanding mine roof fastener



NOV 19, i957 A L. BARRETT 2,813,449

EXPLOSIVELY ACTUATED EXPANDING MINE ROOF' FASTENER Filed April 5, 195o v 2 sheets-sheet 1 Eig-4.

ql; 'Il

ATTORNEY Nov. 1957 A L. BARRETT 2,813,449

EXPLOSIVELY ACTUATED EXPANDING MINE ROOF' FASTENER Filed April 5, 1950 2 Sheets-Sheet 2 QF/ 3. l/"I/gl.

/N VEN TGR:

AllzlzrLeeBarrett A TTORNEY EXPLOSIVELY ACTUATED EXPANDWG MINE RUF )FASTENER A Lee Barrett, Franklin, Pa., assigner to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Penn- Sylvania Application April 5, 1950, Serial No. 154,159

1 Claim. (Cl. 85--40) This invention relates to suspension type roof supports and more particularly to suspension type roof anchors insertible in holes formed in the roof strata of an underground mine or tunnel for binding the roof rock together to minimize flexure and thus prevent rock failure.

From one aspect the invention relates to the bolt structure and its cooperating positioning and expanding means and from another aspect relates to a jack structure for supporting the bolt and the actuator for its expanding means during anchoring of bolts of different lengths.

In underground mines or other underground workings `the roof of the excavation must be supported against `roof falls or cave-ins and it is becoming customary practice to support the roof strata by means of anchor bolts insertible in holes formed in the roof strata and having expansible heads for securing the bolts in position to support the roof rock. Usually suc-h anchor bolts have expansible wedge type heads and threaded rodlike bodies and the heads are expanded to secure the bolts in position and nuts are threaded onto the bolt bodies whereby roof plates or beams may be secured against the roof. In such known types of anchor bolts the bolt heads are expanded by means of pneumatic hammer tools such as stoper drills which drive-in the bolts to effect head expansion, or the bolts may be rst tightened as by power wrenches engaging the nuts to move the tats Patent O bolts axially to effect expansion of the heads and when the bolts are properly set in position further tightening of the nuts on the bolts elfects clamping of the plates or beams against the roof, and it has been found that such methods of setting the bolts and clamping the roof plates or beams are time consuming and that proper setting of the bolts is not assured. The present invention contemplates improvements over such known types of suspension type roof anchors in that improved abutment and expansible anchoring means are provided which may be quickly and effectively operated whereby the bolt may be irmly driven axially into position in the roof strata and then expanded to effect anchoring without the use of pneumatic tools or screw and nut anchoring and tightening devices. The improved anchor bolt of the present invention embodies an improved expansible head structure which may be expanded by a free moving projectile or slug driven axially at high velocity Within the tubular bolt body and the tubular bolt body has an outer end llange which when the bolt is driven axially is moved tightly against the roof plate or beam by the action on the bolt of the projectile or slug prior to expansion of the bolt head. The expansible head of the bolt has a series of internal wedge-shaped annuli secured therein and the tube is split and the projectile or slug which is driven within the annuli of the bolt to eect head expansion, when stopped, lodges within the expanded head to maintain the latter in expanded position and is held against rearward escape from the head, and stop means is provided within the head to preclude` overtravel of the slug. In case the walls of the hole in the roof strata closely surround the expansible bolt head and the roof rock is relatively hard the annuli and tube will be prevented from expanding sufficiently to permit the slug to pass therethrough and under such a condition the annuli due to their structure will deform sufficiently to permit passage of the slug into its full head expanding position. The anchor bolt of the present invention embodies novel means for iirst imparting a powerful inward axial thrust to the bolt to drive the latter up into the roof strata and for only thereafter expanding the bolt head to secure the bolt rmly in place, such operations performed in rapid succession. In accordance with the present invention the bolt is held up in the roof strata by a jack structure and the projectile or slug which is driven axially within the bolt is actuated by a gun adjustably supported by the jack structure and which is positioned at least partially within the tubular bolt and in which an explosive charge is red to actuate an impact element which is movable in the bolt to effect driving of the projectile or slug with considerable force and speed inwardly within the bolt body, and the means whereby an axial driving thrust is imparted to the bolt and for expanding the bolt head are so designed as to permit the projectile or slug to move within the bolt and to lodge within the expanded bolt head to maintain the latter in expanded position. Thus, by the provision of the improved bolt driving and expanding means the roof anchors may be quickly set in place thereby greatly reducing the time consumed in and the cost of the roof supporting function.

It is a primary object of the present invention to provide an improved suspension type roof support for underground mines or tunnels whereby supporting of the roof may be easily and expeditiously elfected. Another object is to provide an improved roof bolt having an improved expansible head structure whereby the bolt may be quickly set and firmly held in roof supporting position. Still another object is to provide an improved tubular anchor bolt which has an expansible head of a novel design and expander means embodying a projectile or slug which is driven inwardly within the bolt bore with considerable momentum or force to effect expansion of the bolt head. A further object is to provide improved displaceable abutment means within the bolt whereby the projectile or slug, as it is driven inwardly, rst imparts an axial thrust to the bolt to effect proper positioning of the bolt in the roof strata and thereafter effects expansion of the head to set the bolt rmly in position thereby eliminating any need for readjustment of the bolt after the latter has been anchored in position. Still another object is to provide an improved anchor bolt which may be quickly set in place in the roof strata by means of a gun which is located at the outer end of the bolt to elfect driving of the latter inwardly and thereafter to elfect expansion of the bolt head. A still further lobject is to provide an improved suspension type roof support having a novel expansible head structure embodying a series of axially spaced, internal annuli welded or otherwise secured `within a tube and which are engaged by a slug driven axially within the bolt to eifect expansion of the bolt head thereby to embed portions of the bolt head into the roof rock, the annuli having internal sloping surfaces so designed that the slug may enter the expansible bolt head and may lodge within the head to maintain the latter in expanded position without the possibility of inadvertent release of the slug. Another object is to provide improved stop means within the expansible head of a bolt of the above character whereby overtravel of the projectile or slug is precluded. A still further object is to provide an improved expansible bolt head having a series of axially spaced wedge-shaped annuli so constructed that in the event the walls of the hole preclude sufficient expansion of the head as the 3 slug enters the head, the annuli will be deformed suiciently to permit the slug to pass therethrough thereby to insure proper gripping of the hole walls. Yet another object is to provide an improved slotted expansible bolt head having elements arranged interiorly of the head at axially spaced points to provide a series of internal restrictions and into which a slug is movable to effect expansion of the head and the restriction-providingelements being so constructed that in the event the head is prevented by the hole walls from expanding sufficiently to permit passage of the slug the elements will deform sufficiently to permit movement of the slug fully Within the head. A still further object is to provide an irnproved adjustable jack structure for holding the bolt and gun in position during the anchoring of the bolt and designed to operate on bolts of varying lengths. These and other objects and advantages of the invention will, however, hereinafter more fully appear.

In the accompanying drawings there are shown for purposes of illustration several forms and modications which the invention may assume in practice.

In these drawings:

Fig. l shows one form of the improved anchor bolt with the bolt placed in position within a hole formed in the roof strata and havin the operating gun and bottom oor jack associated therewith.

Fig. 2 is a view in central longitudinal section taken through the roof bolt, gun, and iiocr jack of Fig. l.

Fig. 3 is a fragmentary sectional View taken on the plane of Fig. 2, showing the projectile or slug in contact with the abutment pin, with the slug imparting an axial thrust to the bolt.

Fig. 4 is a fragmentary sectional View taken on the plane ot Fig. 3 showing the projectile or slug moved part way within the expansible bolt ahead, and the expanding action partially completed.

Fig. 5 is a sectional view similar to Fig. 4 showing the bolt head in fully expanded position, and the projectile or slug at rest.

Fig. 6 is an end view of the improved anchor bolt.

Fig. 7 is a cross-sectional view taken substantially on line '7-7 of Fig. l.

Figs. 8, 9 and l() are sectional views taken on the plane of Fig. 2, showing several modied forms of expansible bolt heads.

Fig. 1l is a sectional view similar to those of Figs. 8, 9 and 10 showing internal annuli of modied construction within the expansible bolt head.

Fig. l2 is a view partially in side elevation and partially in vertical section, showing a modified form of jack structure for the anchor bolt and gun.

The suspension type roof support of the present invention constitutes an improvement in an anchor bolt having displaceable abutment means, an expansible head structure and associated expanding means, wherein, in a preferred embodiment, the bolt is first thrust axially by a projectile or slug to effect driving 4thereof tightly into its permanent position in the roof strata and thereafter the bolt head is expanded by the slug to secure the bolt in place, and stop means is embodied in the head whereby overtravel of the slug is precluded so that the slug lodges in the expanded head to maintain the latter in expanded, Ianchored position. The improved thrust, expansion and stop features all contribute to a common end, but each is of use, and usable, individually.

The improved anchor bolt, as shown in Figs. 1 to 7 inclusive, comprises an elongated tubular body 1 having an integral ange or collar 2 at its outer end, and having its inner end portion formed with an expansible head 3 of a novel design. The expansible bolt head comprises a series of axially spaced annuli or rings 4 secured at 5, as by plug-welding or otherwise, within the bore of the head. These rings are of wedgelike construction and have inner truste-conical bores or openings 6 provided by inclined walls 7 disposed at acute angles and merging upwardly into reduced axial, desirably but not necessarily cylindrical, bores S at their inner ends. The opening of the innermost annulus is relatively reduced as shown so that it provides a stop 8 for the slug to preclude overtravel of the latter, as later made apparent. The bolt head is longitudinally slotted at 9, herein desirably at four equally spaced points, to provide bendable portions 10, and these slots cut through the annuli. Welded or otherwise secured to the outer periphery of the head are rings, exterior annular projections, or collars li, also split, and herein lying in or in adjacency to transverse planes including the upper surfaces l2 of the axially spaced annuli 4 as clearly shown in Fig. 2. These may be formed in any suitable manner, welding material applied to the peripheral surface of the bolt being a satisfactory construction. Secured in aligned holes 13 drilled in the walls of the bolt body are the end portions of a diametric cross pin 14 which provides a displaceable abutment as later described. Below this cross pin is a relatively thin metallic sleeve or collar .i5 herein desirably composed of brass and pressed or otherwise secured within the tube bore. A free moving projectile or slug 16 of tubular construction substantially iits and is guided for movement at high velocity axially within the tube bore and has an axial opening 17 and a tapered inner end 1S. This slug is of slightly greater diameter than the diameters of the bores of the annuli 4 and the sleeve l5, as will later be fully explained.

The anchor bolt of this embodiment is insertible in a hole A formed as by drilling in the roof strata and passes through an opening in a conventional roof plate or cross beam B and is held up in position against the roof by an adjnstabie screw type door jacl; C. Associated with and held in position by the door jack and projecting within the outer end portion of the tube bore is a power actuator' herein a conventional gun D. There is shown, for illustrative purposes, a slight clearance at E between the plate or beam and the root in order that a comparison of Figs. 2 and 3 may indicate that a tightening action of the bolt has taken place in Fig. 3, but it will be understood that normally, prior to the discharge of the gun, the bolt collar 2 is held up tightly against the plate or beam with the latter in engagement with the roof. The i'loor jack C may assume various forms, but as shown comprises a tubular body Ztl having an upper flange 21 abutting the outer end of the bolt as shown in Fig. 1, and threaded at 22 within the jack body is a jack screw 23 provided with an adjustable bottom plate or swiveled foot piece 24. A handle Z5 on the screw is provided t'or tightening the jack to hold the anchor bolt firmly in place during the setting operation. Arranged within the jack body at its upper portion is the gun D which at its bottom rests against a cross bar or pin 26 arranged in and projecting through longitudinal slots 27 formed in the walls of the tubular jack body. A collar 28 threaded at 29 on the exterior of the jack body engages the cross bar and upon upward adjustment of the collar the gun may be firmly held in place with respect to the anchor bolt with its inner portion 3) extending upwardly within the bolt bore as clearly shown in Fig. 2. This gun may assume various forms but herein comprises an elongated actuator rod, plunger or impact element 31 which may be driven upwardly by the tiring of an explosive charge and the almost instantaneous building up of a high gaseous pressure within the gun. The gun has a suitable operator 32 projecting outwardly through a longitudinal slot 33 in the jack body, whereby detonation of the explosive charge may be eiected. The plunger 31 when driven suddenly upwardly drives the projectile or slug 16 upwardly axially within the bore of the anchor bolt. This slug does not attain its maximum velocity instantaneously, and as it moves axially within the bolt first enters the bore of the sleeve 15 and, since it is of larger diameter than the sleeve the latter is fractured and disintegrated, but yet there is provided an upward asienta thrust on the bolt. Substantially simultaneously the slug engages the cross pin 14-while it is still in its process of acceleration and before maximum velocity i-s attainedthereby imparting through the cross pin a powerful axial thrust to the anchor bolt to drive the latter upwardly tightly within the hole. The cross pin 14, as the slug exerts an upward pressure on it, is displaced, fractured or sheared off, and the released slug continues to move axially with still increasing velocity, and as the slug enters the restricted openings of the annuli or rings 4, in the manner shown in Fig. 4, the bendable portions of the split bolt head are expanded outwardly in the manner shown. The slug has imparted to it such a driving force and the annuli are so formed that the slug is driven completely within the head as shown in Fig. 5, in such manner as to enter all of the series of annuli to expand the bendable head portions, thereby to embed the exterior rings lll firmly into the roof rock surrounding the bore hole. The acute-angle surfaces 7 are so arranged that as the slug enters the annuli a substantial lateral force is imparted to the latter and due to the inclination of these surfaces there is relatively small tendency to shearing the annuli from the tube. The projectile or slug .le is prevented from moving too far through the head by the outer restricted annulus 8 and by appropriate fixing of the explosive charge; and, when stopped, lodges within the expanded bolt head as shown in Fig. 5 to maintain the latter in expanded position with the bolt firmly held in place. The annuli 4 grip the periphery of the slug in such a manner that the latter is firmly secured within the upper end of the bolt and has no possible chance to be squeezed outwardly of the bore. Under certain conditions the walls of the hole formed in the roof strata closely surround the expansible head of the bolt and the roof rock is sufficiently hard to prevent full expansion of the annuli 4 and at that time the annuli due to their structure will deform sufficiently to permit passage of the slug therethrough fully within the bolt head thereby to insure proper gripping of the hole walls. When the anchor bolt is firmly set in position in the roof rock the floor jack C and gun D may be removed for reuse in the setting of other anchor bolts in an obvious manner. The anchor bolts are placed at strategic points in the roof strata so as to bind the strata together in such manner as to minimize flexure of the roof rock, thereby to prevent roof failure. The slot 33 is of `Sufficient width so that when the collar 28 is threaded downwardly on the jaclt the gun may be removed from the bolt and released bodily from the jack through the slot 33. By proper adjustment of the collar 28 relative to the jack the gun may be positioned axially relative to the anchor bolt so as to operate on bolts of different lengths.

In the several modifications shown in Figs. 8, 9 and l0 the exterior annular projections or rings 11 of the rst embodiment `are arranged at different locations axially of the tube of the expansible bolt head so as to vary the gripping action of the head on the walls of the hole. In Fig. 8 external annuli or rings 11a are secured as by welding or otherwise upon the external periphery of the tube at points spaced oppositely from the lines along which the surfaces 7 of the frusto-conical bores 6 merge with the cylindrical axial bores 8. With such an arrangement the external rings are located at points where the maximum lateral pressure is imparted by the slug or plunger 16 as the latter is driven into the internal annuli 4 thereby to effect firm embedding of the external annuli within the hole walls. In Fig. 9 external rings 11b are secured to the external periphery of the tube of the bolt head at points opposite the portions of maximum internal diameter of the internal annuli 4 so that greater flexibility is obtained in the event the external rings expand against hard rock providing the hole walls, thereby providing greater freedom of expansion or yieldability .of the tube when the slug is driven into the internal annuli. In Fig. 10 external rings 11e are located upon the exterior periphery of the tube at points opposite the internal spaces between the internal annuli 4 so that there is provided still greater flexibility to bending of the expansible head upon driving of the slug within the internal annuli 4. Since the external rings are disposed intermediate the internal annuli the walls of the tube are free to bend or yield inwardly, thus increasing the flexibility of the expansible head particularly when the head is positioned in hard rock. Evidently, the external rings and the internal annuli may be arranged on the tube in various other relations.

In Fig. ll the internal annuli are somewhat modified. In this embodiment internal annuli 4a are secured as by welding or otherwise within the bore of the tube of the split bolt head and, in this construction, the three inner annuli are wholly of wedge shape having in radial section, truste-conical bores 35 which extend to the upper transverse surfaces 36 of the annuli. When the anchor bolt is closely tted in a hole formed in the roof strata and the roof rock surrounding the hole is relatively hard, the slug or plunger 16 as it is driven inwardly within the bolt enters the annuli successively and when the rock prevents further expansion of the tube the internal annuli are deformed and at least partially flattened out by the slug as shown, as the slug passes therethrough. Due to the particular shape of the internal annuli, the upper portions thereof may bend or flatten as the slug enters the same. Other cross sections suited to the accomplishment of the mode of operation hereinabove described may be substituted for those particularly illustrated.

In the embodiment of the invention shown in Fig. l2 a modified jack structure for the anchor bolt and gun is disclosed. A screw type oor jack has a tubular body 3S which has an internal bore at 39 to receive a jack screw d@ telescopically arranged within the tubular body. Threadedly engaging the jack screw is an adjusting nut 41 having a handle 4l whereby the tubular body 38 may be adjusted axially with respect to the screw. The jack screw has an offset lower portion 42 provided with a swiveled foot piece 43. Secured as by welding to the tubular jack body and arranged in parallelism therewith is a tubular member 44 which is longitudinally slotted at 45 along its outer Wall. The upper end of the tubular member 44 has an abutment plate 46 which is engageable with the collar 2 of the anchor bolt for holding the latter up in the hole A formed in the roof strata. An elongated gun D is insertible laterally through the slot 45 in the tubular member 44 within the latter and is adapted to be moved upwardly within the bore of the anchor bolt. Formed in the walls of the tubular member along the length of the latter are spaced holes 47 and a pin 48 is insertible in the desired one of these holes to provide a bottom support for the adjustible gun D. The operator 32 of the gun may provide a suitable handle whereby the gun may be readily manually adjusted axially within the tubular member 44 and the anchor bolt. By the provision of this wide range of adjustment of the gun the latter may be associated with anchor bolts having a relatively wide variation in length. Other known forms of adjustment for the gun relative to the jack may be employed in lieu of the series of holes and pin.

A feature of the invention which is not perhaps as fully noted above as may be desirable, resides in the capacity of the bolt to be used in holes effectively notwithstanding there may be a reasonable variation of the hole diameter from the external diameter of the tube which forms the bolt. It will be noted that in the bolt structure of Fig. 10, the external annuli llc are arranged at points intermediate the internal annuli 4, so that when the projectile or slug 16 is driven successively into the internal annuli the split tube portion of the bolt head is expanded to bring the external annuli into firm contact with the walls of the hole, and the portions of the split tube opposite the internal annuli are bulged laterally as shown,

to embed exterior portions thereof into the walls of the hole. When the holes are formed in a relatively hard formation, and the external annuli 11C are closely fitted in the hole and expanded into contact with the hole walls, due to the location of the external annuli of this embodiment, the tube Walls are free to flex. Thus, even when the hole diameter varies and the hole is formed in a relatively hard formation the bolt head may be expanded to effect an anchoring of the bolt in the roof strata, due to the arrangement noted above and as a result the need for very fine adaptation of roof drills to bolt sizes is avoided. In the forms of the invention where the external annuli are at points opposite the internal annuli 4 only very limited expansion could be effected and the internal annuli may be substantially deformed or flattened out as the slug is driven into place.

To summarize briefly, the bolt will be pressed by the jack as far as possible upwardly before the gun is discharged. When such discharge occurs, the accelerating, but still not at full velocity, projectile or slug will, through the frangible sleeve 15 and the displaceable pin 14, pull the bolt upwardly and eliminate all loosenessif there has been any-between the head 2 and the element B, and between the latter and the surface of the roof. Thereafter the slug will expand the several split rings and the portions of the split tube to which such rings are secured, the action being effected by virtue of the continued thrust of the explosive charge and the momentum of the slug at its high velocity. The explosive charge of the gun will be predetermined so that the slug will desirably expand each of the split rings, but be unable to expand the final ring sufficiently to pass through As a result of this invention an improved suspension type roof support is provided which may be quickly and expeditiously set in place in the roof strata thereby greatly reducing the time consumed in and the cost of supporting the roof of an underground excavation. By the provision of the improved expansible head structure and the cooperating internal abutment means the bolt iS initially moved axially-if motion is possible-so that the bolt will be so positioned in the roof strata that the plate or beam will be pressed hard against the roof, and thereafter the bolt head is expanded so that the bolt is firmly held in positon without the need of separate readjustment for tightening purposes and Without the danger of appreciable slippage. The projectile or slug is riven by the gun with considerable force within the bolt bore to effect axial tightening of the bolt and expansion of the bolt head, and the projectile or slug when lodged within the head serves to maintain the latter in expanded position. By the provision of the series of internal annuli or rings secured within the bolt head and the inclined surfaces within the rings the bolt head is effectively expanded and the slug is rrnly retained within the expanded head by the internal surfaces of the annuli,

c, so that there is little tendency towards escape of the slug and inadvertent release of the bolt. The adjustable jack structure firmly holds the bolts in position in the roof strata and provides a convenient adjustable support for the expander gun whereby the latter may operate on bolts of varying lengths. These and other advantages of the invention will be clearly apparent to those skilled in the art.

While there are in this application specifically described several forms and modifications which the invention may assume in practice, it will be understood that these forms and modifications of the same are shown for purposes of illustration and that the invention may be further modified and embodied in various other forms Without departing from its spirit or the scope of the appended claim.

What l claim as new and desire to secure by Letters Patent is:

ln a suspension type roof support, an elongated tubular anchor bolt insertable in a hole formed in the roof strata, said bolt having an axial bore of substantial length and an expansible head at its inner end, said head having a series of axially spaced restrictions therein of smaller internal dimensions than said bore, and the innermost restriction being smaller than the others, and a free moving projectile substantially fitting said bore and movable axially with substantial speed under the inuence of an expansive power charge within said bore of the bolt and said projectile engaging and progressively entering said other less-restricted restrictions to expand said head into gripping contact with the hole-walls, said projectile as it reaches the end of its travel engaging the innermost smaller restriction and the latter providing a positive stop for said projectile to preclude overtravel of the latter to cause said projectile to lodge Within the expanded head to maintain the latter in expanded position.

References Cited in the file of this patent UNITED STATES PATENTS 1,191,151 Brush July 18, 1916 1,277,370 Bovard Sept. 3, 1918 1,587,317 Horton June 1, 1926 1,806,640 Ogden May 26, 1931 1,848,142 Peirce Mar. 8, 1932 1,918,745 Forsythe July 18, 1933 1,994,210 Chobert Mar. 12, 1935 2,146,923 Wahlstrom Feb. 14, 1939 2,199,605 Baker May 7, 1940 2,292,467 Norsell Aug. 11, 1942 2,296,817 Gartin Sept. 22, 1942 2,296,819 Osgood Sept. 22, 1942 2,313,402 Turechek Mar. 9, 1943 2,353,851 Rosan July 18, 1944 2,421,769 Wolfe June 10, 1947 2,448,351 Brush Aug. 31, 1948 2,601,803 Newman July 1, 1952 

